Ridding brassicas of pests

I have been advised that spraying my brassicas with salt water will rid them of pests. I this correct and if so, how strong should the solution be? Can you advise please or come up with successful tried and tested remedies? Thank you.

I wash all my brassicas in salty water before cooking, to make all the caterpillars float to surface.

If you use salt on them while they are still in the ground, you will probably kill the plant.

If you can see caterpillars, pick them off. netting against the butterflies is the only way you will keep them free of caterpillars , unless you want to use a chemical spray. (Provado fruit and veg spray)

My brassicas have been eaten to bits this year. I used collars but everything went down hill in August . Plan to use netting next year what about fleece? do you just lay it over the plants. My sprouts are looking good I've cut off badly infected leaves. Good idea or not?